Application In Organic Solar Cells Research Articles

Facile access to C-N bonds via unexpected side reactions of Knoevenagel condensation and their application in high-efficiency organic solar cells

Facile access to C-N bonds via unexpected side reactions of Knoevenagel condensation and their application in high-efficiency organic solar cells

Low‐Cost Pentacyclic Nonfullerene Acceptors to Exceed 13% Efficiency by Thermal Annealing‐Free Treatment

Nonfullerene electron acceptors (NFAs) improve the photoelectrical conversion efficiency of organic solar cells (OSCs), but they suffer from high synthetic cost and time‐consuming thermal annealing treatment. Nevertheless, low‐cost NFAs and simple device fabrication are still crucial issues to boosting the commercial application of OSCs. Herein, one kind of low‐cost pentacyclic NFAs based on benzothiadiazole and thiophene derivatives named L1‐EH and L1‐BO with different substitutions is successfully synthesized and characterized. The optimized OSCs based on PM6:L1‐BO (2‐butyloctyl side chain) display an outstanding power conversion efficiency of 13.15%. Moreover, OSC devices based on these acceptors operate in thermal annealing‐free conditions. Further studies manifest that the proper side chains in NFAs can induce more favorable face‐on molecule orientation, enhance carrier mobility, balance charge transport, and reduce recombination losses. This research demonstrates that these types of low‐cost NFAs are promising active layer candidates of high‐efficiency organic solar cells featuring simple device manufacture.

Ductile Oligomeric Acceptor-Modified Flexible Organic Solar Cells Show Excellent Mechanical Robustness and Near 18% Efficiency.

High power conversion efficiency (PCE) and mechanical robustness are key requirements for wearable applications of organic solar cells (OSCs). However, almost all highly efficient photoactive films comprising polymer donors (PD ) and small molecule acceptors (SMAs) are mechanically brittle. In this study, highly efficient (PCE = 17.91%) and mechanically robust (crack-onset strain [COS] = 11.7%) flexible OSCs are fabricated by incorporating a ductile oligomeric acceptor (DOA) into the PD :SMA system, representing the most flexible OSCs to date. The photophysical, mechanical, and photovoltaic properties of D18:N3 with different DOAs are characterized. By introducing DOA DOY-C4 with a longer flexible alkyl linker and lower polymerization, the D18:N3:DOY-C4-based flexible OSCs exhibit a significantly higher PCE (17.91%) and 50% higher COS (11.7%) than the D18:N3-based device (PCE = 17.06%, COS = 7.8%). The flexible OSCs based on D18:N3:DOY-C4 retain 98% of the initial PCE after 2000 consecutive bending cycles, showing greater mechanical stability than the reference device (maintaining 89% of initial PCE). After careful investigation, it is hypothesized that the enhancement in mechanical properties is mainly due to the formation of tie chains or entanglement in the ternary blend films. These results demonstrate that DOAs have great potential for achieving high-performance flexible OSCs.

Exploring novel naphthalene-fused octacyclic core-based non-fullerene acceptor materials with augmented optoelectronic attributes for stable and efficient solar cells

To meet the growing need for high-efficiency photovoltaic materials in today's high-tech applications, ten acceptor molecules (SH01-SH10) with naphthalene-fused octacyclic electron-donating central core NITT are proposed. End-capped structural-alterations on reference R (NITT-2F) with strong electron-drawing groups (A01-A10) are performed for attaining improved optoelectronic characteristics and possible applications in organic solar cells (OSCs). In comparison to the reference R (NITT-2F), key parameters such as FMO analysis, energy gap (Egap), open-circuit voltage (VOC), absorption spectra (λmax), excitation energy (Ex), transition density matrix (TDM) with binding energy (Eb), the density of states (DOS), reorganization energy of the electron (λe) and hole (λh), and charge transfer with PM6 donor substance are perceived. It is found that all proposed molecules (SH01-SH10) have a reduced energy gap (2.104–1.901 eV), a broader absorption spectrum (707–820 nm), and smaller excitation energy (1.75–1.51 eV) as compared to reference molecule NITT-2F values 2.132 eV, 675 nm and 1.79 eV respectively. The significant charge transfers and 0.23 eV decrease in the Egap is noted for the designed molecule SH05. Results confirmed that all proposed molecules, especially SH05 could be an excellent choice for OSCs candidate due to the combination of strong electron-withdrawing effect in end-capped acceptor unit and extended conjugation, as well as its promising photovoltaic properties, which include the lowest Egap (1.901 eV), highest λmax (820 nm (in chloroform) and 729 nm (in gas phase)) with Ex values of 1.51 and 1.70 eV respectively, slightest electron mobility (λe = 0.0090 eV) and hole mobility (λh = 0.0073 eV), highest ionization potential (6.826 eV) and electron affinity (3.384 eV), and fine value of VOC=1.02 V with respect to (ǀEPM6HOMOǀ - ǀESH05LUMOǀ). End-capped acceptor alterations are an acceptable way to attain the desired optoelectronic characteristics demonstrated in this research work. This study can be essential in achieving efficient novel non-fullerene OSCs with higher performance, low cost, and higher optical absorption coefficient. Thus, proposed molecules (SH01-SH10) with proficient electron and hole transfer mobilities and optoelectronic features are recommended to develop higher-efficiency solar cells.

Stability enhancement of silver nanowire-based flexible transparent electrodes for organic solar cells

Flexible organic solar cells (OSCs) are one of the most promising power sources for wearable electronics. A high-quality transparent electrode is one of the indispensable components for OSCs because it guarantees sufficient light transparency and electrical conductivity. Silver nanowires (AgNWs) are considered to be an ideal candidate over commercial rigid indium tin oxide as flexible transparent electrodes (FTEs) because of their superior optoelectronic properties, excellent mechanical flexibility, solution treatability, and high compatibility with semiconductors. However, the stability of AgNWs-based FTEs (AgNWs-FTEs) hinders their further application. In this perspective, we provide state-of-the-art solution-processed AgNWs with enhanced stability and their applications in flexible OSCs. We start with a systematic analysis of the failure mechanisms and evaluation methods of AgNWs-FTEs. Then the key reinforced materials are summarized. Next, the main stability enhancement strategies are briefly discussed. Applications of AgNWs-FTEs in flexible and stretchable OSCs are further surveyed. Finally, an outlook on the current status, future challenges, and emerging strategies in this field is presented.

Ultra Robust and Highly Efficient Flexible Organic Solar Cells with Over 18 % Efficiency Realized by Incorporating a Linker Dimerized Acceptor.

The wearable application of flexible organic solar cells (f-OSCs) necessitates high power conversion efficiency (PCE) and mechanical robustness. However, photoactive films based on efficient non-fullerene small molecule acceptors (NF-SMAs) are typically brittle, leading to poor mechanical stability in devices. In this study, we achieved a remarkable PCE of 18.06 % in f-OSCs while maintaining ultrahigh mechanical robustness (with a crack-onset strain (COS) of higher than 11 %) by incorporating a linker dimerized acceptor (DOY-TVT). Compared to binary blends, ternary systems exhibit reduced non-radiative recombination, suppressed crystallization and diffusion of NF-SMAs, and improved load distribution across the chain networks, enabling the dissipation of the load energy. Thus, the ternary f-OSCs developed in this study achieved, high PCE and stability, surpassing binary OSCs. Moreover, the developed f-OSCs retained 97 % of the initial PCE even after 3000 bending cycles, indicating excellent mechanical stability (9.1 % higher than binary systems). Furthermore, the rigid device with inverted structure based on the optimal active layer exhibited a substantial increase in efficiency retention, with 89.6 % after 865 h at 85 °C and 93 % after more than 1300 h of shelf storage at 25 °C. These findings highlight the potential of the linker oligomer acceptor for realizing high-performing f-OSCs with ultrahigh mechanical robustness.

Ultra Robust and Highly Efficient Flexible Organic Solar Cells with Over 18 % Efficiency Realized by Incorporating a Linker Dimerized Acceptor

AbstractThe wearable application of flexible organic solar cells (f‐OSCs) necessitates high power conversion efficiency (PCE) and mechanical robustness. However, photoactive films based on efficient non‐fullerene small molecule acceptors (NF‐SMAs) are typically brittle, leading to poor mechanical stability in devices. In this study, we achieved a remarkable PCE of 18.06 % in f‐OSCs while maintaining ultrahigh mechanical robustness (with a crack‐onset strain (COS) of higher than 11 %) by incorporating a linker dimerized acceptor (DOY‐TVT). Compared to binary blends, ternary systems exhibit reduced non‐radiative recombination, suppressed crystallization and diffusion of NF‐SMAs, and improved load distribution across the chain networks, enabling the dissipation of the load energy. Thus, the ternary f‐OSCs developed in this study achieved, high PCE and stability, surpassing binary OSCs. Moreover, the developed f‐OSCs retained 97 % of the initial PCE even after 3000 bending cycles, indicating excellent mechanical stability (9.1 % higher than binary systems). Furthermore, the rigid device with inverted structure based on the optimal active layer exhibited a substantial increase in efficiency retention, with 89.6 % after 865 h at 85 °C and 93 % after more than 1300 h of shelf storage at 25 °C. These findings highlight the potential of the linker oligomer acceptor for realizing high‐performing f‐OSCs with ultrahigh mechanical robustness.

A comprehensive analysis of charge transfer effects on donor-pyrene (bridge)-acceptor systems using different substituents.

The alternant polycyclic aromatic hydrocarbon pyrene has photophysical properties that can be tuned with different donor and acceptor substituents. Recently, a D (donor)-Pyrene (bridge)-A (acceptor) system, DPA, with the electron donor N,N-dimethylaniline (DMA), and the electron acceptor trifluoromethylphenyl (TFM), was investigated by means of time-resolved spectroscopic measurements (J. Phys. Chem. Lett. 2021, 12, 2226-2231). DPA shows great promise for potential applications in organic electronic devices. In this work, we used the ab initio second-order algebraic diagrammatic construction method ADC(2) to investigate the excited-state properties of a series of analogous DPA systems, including the originally synthesized DPAs. The additionally investigated substituents were amino, fluorine, and methoxy as donors and nitrile and nitro groups as acceptors. The focus of this work was on characterizing the lowest excited singlet states regarding charge transfer (CT) and local excitation (LE) characters. For the DMA-pyrene-TFM system, the ADC(2) calculations show two initial electronic states relevant for interpreting the photodynamics. The bright S1 state is locally excited within the pyrene moiety, and an S2 state is localized ~0.5 eV above S1 and characterized as a donor to pyrene CT state. HOMO and LUMO energies were employed to assess the efficiency of the DPA compounds for organic photovoltaics (OPVs). HOMO-LUMO and optical gaps were used to estimate power conversion and light-harvesting efficiencies for practical applications in organic solar cells. Considering the systems using smaller D/A substituents, compounds with the strong acceptor NO2 substituent group show enhanced CT and promising properties for use in OPVs. Some of the other compounds with small substituents are also found to be competitive in this regard.

Molecular design of D-π-A-π-D small molecule donor materials with narrow energy gap for organic solar cells applications.

Developing novel materials present a great challenge to improve the photovoltaic performance of organic solar cells (OSCs). In this paper, we designed a series of the donor-π bridge-acceptor-π bridge-donor (D-π-A-π-D) structure molecules. These molecules consist of diketopyrrolopyrrole (DPP) moiety as core, 9-hexyl-carbazole moiety as terminal groups, and different planar electron-rich aromatic groups as π-bridges. The density functional theory (DFT) and time-dependent DFT (TD-DFT) computations showed that the frontier molecular orbital (FMO) energy levels, energy gaps, electron-driving forces (ΔEL-L), open-circuit voltage (Voc), fill factor (FF), reorganization energy (λ), exciton binding energy (Eb), and absorption spectra of the designed molecules can be effectively adjusted by the introduction of different π-bridges. The designed molecules have narrow energy gap and strong absorption spectra, which are beneficial for improving the photoelectric conversion efficiency of organic solar cells. In addition, the designed molecules possess large ΔEL-L, large Voc, and FF values and low Eb when the typical fullerene derivatives are used as acceptors. The FMO energy levels of the designed molecules can provide match well with the typical fullerene acceptors PC61BM, bisPC61BM, and PC71BM. Our results suggest that the designed molecules are expected to be promising donor materials for OSCs. All DFT and TD-DFT calculations were carried out using the Gaussian 09 code. The computational technique chosen was the hybrid functional B3LYP and the 6-31G(d,p) basis set. The benzene and chloroform solvent effects have been considered using the polarized continuum model (PCM) at the TD-DFT level. The simulated absorption spectra of designed molecules were plotted by using the GaussSum 1.0 program.

Green-Processed Non-Fullerene Organic Solar Cells Based on Y-Series Acceptors.

The development of environmentally friendly and sustainable processes for the production of high-performance organic solar cells (OSCs) has become a critical research area. Currently, Y-series electron acceptors are widely used in high-performance OSCs, achieving power conversion efficiencies above 19%. However, these acceptors have large fused conjugated backbones that are well-soluble in halogenated solvents, such as chloroform and chlorobenzene, but have poor solubility in non-halogenated green solvents. To overcome this challenge, recent studies have focused on developing green-processed OSCs that use non-chlorinated and non-aromatic solvents to dissolve bulk-heterojunction photoactive layers based on Y-series electron acceptors, enabling environmentally friendly fabrication. In this comprehensive review, an overview of recent progress in green-processed OSCs based on Y-series acceptors is provided, covering the determination of Hansen solubility parameters, the use of non-chlorinated solvents, and the dispersion of conjugated nanoparticles in water/alcohol. It is hoped that the timely review will inspire researchers to develop new ideas and approaches in this important field, ultimately leading to the practical application of OSCs.

Optical and electrical evaluation of a nylon 11-ZnO film incorporation in disodium phthalocyanine heterostructures

Disodium phthalocyanine (Na2Pc) has been considered as promising organic semiconductor for optoelectronic applications, however, Na2Pc-based devices are not being fully studied. To study the Na2Pc as active layer for optoelectronic devices, and also the effect of the incorporation of a nylon 11-ZnO film within the device heterostructure, in this work two heterojunction cells of Ag/Na2Pc + TCNQ/triphenylamine/p-Si/Al and Ag/nylon 11-ZnO/Na2Pc + TCNQ/triphenylamine/p-Si/Al were fabricated by vacuum thermal evaporation technique. The topography of the heterostructures was analyzed by atomic force microscopy. Later, the films that form the heterostructure were optically characterized by Ultraviolet-visible spectroscopy and the optical band gap and the Urbach energy were obtained. The values of the optical gap for the films are between 2.08 and 2.93 eV. The value of Urbach energy is lower for the pristine triphenylamine film, and higher for the film composed of nylon and ZnO. Moreover, the two heterostructures present a strong photoluminescence in the visible region. On other hand, by introducing the nylon 11-ZnO film in the heterostructure shows an important increase of the short circuit current density (Jsc), conductivity and photocurrent values, indicative of a better mobility and more carriers generation. For this heterostructure a mean 79.7% external quantum efficiency and 0.48 mA/cm2 Jsc were obtained. These results indicate that these heterostructures can be used toward organic solar cell applications and remark on the large effect of the nylon 11-ZnO dielectric film addition on their performance.

A DFT Study of Bridge-Driven Engineering of Non-Fullerene-Based Acceptors for Efficacious Organic Solar Cell Applications

The structural, optical, electronic and photovoltaic properties of non-fullerene molecular entity were analyzed by using density functional theory method MPW1PW91/6-31G (d, p). The simulated results of all the modeled molecules proved them as more efficient molecules for practical use in organic solar cell. Their good solution process-ability and interface (new modeled molecules: PBDBT) success made high value fill factor and open circuit voltage. Comparatively, BDCl2F-DS was proved to be an outstanding material with open-circuit voltage (1.71[Formula: see text]eV) and fill factor (92.25%). Assumption of a similar value of short circuit current from the reference work PCE was estimated. By doing so, outstanding calculated PCE values (in the range of 27.36% to 33.76%) made newly modeled molecules an advancement in investigation of unfused non-fullerene acceptors.

Porphyrin and phthalocyanine heavy metal removal: overview of theoretical investigation for heterojunction organic solar cell applications.

Heavy metals are highly noxious, and their presence can cause diverse effects on living organisms and the environment. Crown ether porphyrins and phthalocyanines are known to effectively extract these pollutants and are also used in photovoltaic devices. This study aims to evaluate various factors that govern intramolecular charge transfer (ICT) and photo-injection processes, including maximum absorption wavelength (λmax), density of states (DOS), charge transfer dipole (μCT), light harvesting efficiency (LHE), open-circuit voltage (Voc), and free energy change of electron injection (ΔGinj) in order to investigate the performance of different compounds designed from metalloporphyrins for bulk-heterojunction organic solar cell (BHJ-OSC) applications. The porphyrin complex showed the best optoelectronic properties, with remarkable LHE values and CT amounts compared to phthalocyanine derivatives. The central metal played a significant role in optimizing the optical properties of the materials for use in solar cells. HgPr4O and CdPr4O were found to have optimal Voc values, resulting in effective injection, high electron, and hole mobilities, making them ideal materials for highly efficient BHJ-OSC devices. Density functional theory (DFT) approach was employed with the B3LYP functional and the def2TZVP basis set as implemented in the Gaussian 16 revision C.01 program to investigate the designed complexes and to compute geometrical parameters, frontier molecular orbitals (FMOs), and natural bond orbital (NBO). Furthermore, the time-dependent density functional theory (TD-DFT) method was used to analyze the optical properties and photovoltaic characteristics of selected metalloporphyrins by examining the UV-Vis spectra. In summary, the study presents a thorough description of the structural and electronic properties of the investigated complexes and provides insights into their potential use in photovoltaic applications.

Oligomerized Fused-Ring Electron Acceptors for Efficient and Stable Organic Solar Cells.

Organic solar cells (OSCs) have attracted wide research attention in the past decades. Very recently, oligomerized fused-ring electron acceptors (OFREAs) have emerged as a promising alternative to small-molecular/polymeric acceptor-based OSCs due to their unique advantages such as well-defined structures, batch reproducibility, good film formation, low diffusion coefficient, and excellent stability. So far, rapid advances have been made in the development of OFREAs consisting of directly/rigidly/flexibly linked oligomers and fused ones. In this minireview, we systematically summarized the recent research progress of OFREAs, including structural diversity, synthesis approach,molecular conformation and packing, and long-term stability. Finally, we conclude with future perspectives on the challenges to be addressed and potential research directions. We believe that this review will encourage the development of novel OFREAs for OSC applications.

Addition of acceptor moiety toward Quinoxaline-based conjugated framework of chromophores for highly efficient organic solar cells

The quantum contemplation of highly unsaturated D-π-A type renewed chromophores (TQ41-TQ45) constructed on quinoxaline core-based model TQ4 are predicted to suggest novel photovoltaic constituents for the application of organic solar cells. The model TQ4 was amended by the replacement of terminal groups with conjugated acceptors via thiophene to design five novel chromophores and their structural as well as optoelectronic attributes were calculated at selected DFT method PBEPBE/6-31G (d, p) level of theory. FMO study revealed that high charge transfer occurred between HOMO-LUMO by the reduction of energy gap up to 0.59 eV (for TQ44) which is quite low from the model TQ4 (2.04 eV). Absorption profile unveiled that the maximum absorption of all the designed chromophores in dichloromethane was in visible and near IR region exhibiting bathochromic shift up to 916 nm that is higher than the reference TQ4 (505 nm). Higher values of dipole moment by novel chromophores up to 16.85 D than reference (1.66 D) suggested good solvation and better molecular packing. ESP analysis revealed electron distribution on various parts of the molecules by colored maps that is found to be effective for better ICT. TDM plots depicted density of electron transitions on various molecular sites by the absorption of light. RE values of electron and hole for novel molecules proved to be highly efficient that enhanced the charge mobilities and prevented charge recombination. Finally, open circuit voltage of all the studied chromophores was calculated by scaling our designed donors to the well-known acceptor PC71BM that is very effective for the fabrication of elite organic solar cells.

Polycyclic Aromatic Lactam‐Like Donors Synthesized upon C─H Activation Strategy for High‐Efficiency Ternary Organic Solar Cells

The rapidly developed organic solar cells (OSCs) are largely driven by π‐conjugated small‐molecule and polymer materials in recent years. However, the organic photovoltaic materials served as the active layer are typically synthesized by multistep Stille or Suzuki cross‐coupling reaction, which are neither cost‐efficient nor atom‐economic, and may bring toxicity concerns. Thus, it is imperative to develop easily accessible materials that do not involve organotin and organoboron reagents to promote the commercial application of OSCs. Herein, three small‐molecule donors (Ph‐RDN, N‐RDN, and TT‐RDN) comprising polycyclic aromatic lactams (PAL) core are designed and synthesized by direct C─H activation strategy and employed as the third components into the model PM6:Y6 photovoltaic systems. These donors show low‐lying highest occupied molecular orbital energy levels, good crystallinity, and complementary absorption with the host system (PM6:Y6). The optimized ternary devices achieve higher power conversion efficiency (PCE) (17.01% for PM6:Ph‐RDN:Y6, 16.58% for PM6:N‐RDN:Y6, and 17.00% for PM6:TT‐RDN:Y6) as compared with PM6:Y6 binary devices (15.67%), which are attributed to the higher charge mobilities, the more balanced charge transport, and the optimized morphology with a more well‐defined fibrillar network. Therefore, PAL‐based small‐molecule donors, as a class of “greener” organic photovoltaic materials, can enhance the PCE of state‐of‐the‐art OSCs.

Small thiophene-based molecules with favorable properties as HTMs for perovskite solar cells or as active materials in organic solar cells

Computational investigations are carried out to design new molecules based on thiophene cores substituted in several positions using different end-capped electron-donating groups formed from triphenylamine or OMe-triphenylamine that can be used as HTMs in Perovskite Solar Cells (PSCs), or as an active layer in Organic Solar Cells. The influence of π-extension on the charge transfer process is also probed by inserting two azomethine groups between acceptor and donor (D-π-A-π-D) moieties. The designed molecules (T10,12,13,15) were compared with the two synthesized molecules (T11,14) that have been applied as HTMs in a PSC. Density functional theory (DFT) and time-dependent DFT (TD-DFT) were chosen to calculate different chemical parameters of these molecules. Different chemical parameters were calculated to make the link between geometrical parameters and the efficiency, solubility, and stability of the under-probed compounds. The results show that all molecules can be used adequately with the perovskite matrix because of their sufficient deep HOMOs levels. The optoelectronic properties of the D-A-D molecules show no competition with the light-harvesting of the perovskite layer, while D-π-A-π-D compounds show a slight overlap with the absorption band of perovskites. All molecules indicate a faster hole-transport rate and an easy electron-hole pairs dissociation into free charge carriers, which facilitates the hole transport and enhances open-circuit voltage. Adding a second thiophene unit in the central core reinforces the structure's flexibility and improves Frontier Molecular Orbital's electronic density distribution, while inserting azomethine groups is advantageous for the molecule's solubility. Their short gaps, higher radiative lifetimes, and visible light absorbance make T12,15 good candidates for their usage in organic solar cell applications. A spontaneous solvation process within dichloromethane for all the investigated molecules was proved based on the high negative free energies.

Computer aided design and evaluation of benzothiadiazole based non-fullerene acceptors for organic solar cells applications

Herein, we report the end-capped modification of the recently reported acceptor CH1007. Considering the importance of non-fullerene acceptors, we theoretically designed a series of benzo-thiadiazole core-based acceptors (MS1-MS8) to enhance the photophysical, and photovoltaic properties of the acceptors. In this study, properties like frontier molecular orbitals, maximum absorption, transition density matrix, open-circuit voltage, binding and excitation energies, dipole moment, and partial density of states were estimated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using B3LYP functional with bases set 6-31G(d,p). When studied computationally, all engineered compounds exhibited red-shift in the absorption spectrum and λmax lie in the range of 734–900 nm, compared to the reference compound (λmax = 735 nm). The designed acceptors exhibited low reorganizational energies (better charge transfer property), low binding and excitation energies besides narrow HOMO-LUMO bandgap. Moreover, the donor–acceptor complexes of the designed acceptors MS1 and MS4 have been studied with well-known standard donors PTB7-Th & PM6. The distribution of electron density in the resultant donor–acceptor complexes showed successful shift of electron density from donor moiety to acceptor moiety. The results revealed that such type of end-capped modifications in acceptors can lead to better photophysical and optoelectronic properties. So, designed compounds have potential to enhance the capacity of acceptor molecules and are therefore, suggested for the development of more efficient organic solar cells (OSCs).

Carbazole Derivative Doped Polyoxometalate Inorganic Clusters as Hole Transport Layer to Enhance the Photovoltaic Performance of Organic Solar Cells

Polyoxometalate inorganic clusters (PICs) as a kind of environmentally friendly material can potentially act as an effective hole transport layer (HTL) in organic solar cells (OSCs) due to their thermally stable, low-cost, easily soluble, and excellent redox properties. However, their low conductivity often limits the applications in high-efficiency OSCs. Here, we use a carbazole derivative (2PACz) to modify the bivalent tin (Sn2+) doped phosphomolybdic acid (H3PMo12O40) (termed HPMO-Sn) to further increase the conductivity. The resulted HPMO-Sn:2PACz HTL displays an improved hole transport ability, enhanced conductivity, increased exciton dissociation efficiency, and low nonradiative energy loss in OSCs. As a result, OSCs employing HPMO-Sn:2PACz as the HTL and PM6:Y6 as the active layer exhibit higher power conversion efficiency (17.62%) than those using HPMO-Sn (efficiency: 16.40%) or PEDOT:PSS (efficiency: 16.45%) as the HTL with enhanced open-circuit voltage and fill factor. Our results provide an effective method to elevate the conductivity of PICs and demonstrate the possibility of using the modified PICs as an effective HTL to achieve high-efficiency OSCs.

The Optical Energy Gap of the Semiconducting Intrinsic Layer for Organic Solar Cell Applications

The optical energy gap of the semiconducting intrinsic layer plays a crucial role in determining the increase in efficiency. The carbon-based biomass can be a choice for the silicon used as solar cell material. Here, we proposed the best biomass that can be used as a semiconductor component in solar cell applications. Coconut shells as bio-waste and palmyra sap, which are available in most areas of Indonesia, can be the best candidates to be considered. The XRD measurement showed both organic materials have an amorphous phase. The coconut shells sample has two peaks that are identical to graphene peaks, therefore this material is called graphenic-like carbon (GC). Furthermore, from the UV-visible spectroscopy, it was shown that both materials have a high transmittance of more than 95%, which indicates that they have transparent properties. Also, the Tauc plot method gives information about the optical energy gap of coconut shell charcoal (GC) and palmyra sap (a:C) which are 2.67 and 1.83 eV, respectively. From this result, palmyra sap becomes promising material to be applied as an intrinsic layer for semiconducting components in solar cell applications.Keywords: Amorphous phase, Coconut shells charcoal, Optical energy gap, Palmyra sugar.