Two-dimensional Bi2OS2 doping improves the performance and stability of perovskite solar cells

High-performance methylammonium-free ideal-band-gap perovskite solar cells

Organometal hybrid perovskite material has emerged as an attractive competitor in the field of photovoltaics due to its promising potential of low-cost and high-efficiency photovoltaic applications. Although organometal halide perovskite solar cell shows great potential to meet future energy needs, the degradation raises serious questions about its commercialization viability. At present, the stability of perovskite solar cells has been studied in various environmental conditions. Nonetheless, an understanding of the degradation and its performance of CH3NH3PbI3-xClx perovskite solar cell is limited. Herein, we report the mechanical and structural degradation of CH3NH3PbI3-xClx perovskite films at room temperature as a function of time and thermal instability of perovskite solar cells during the heating and cooling processes. For mechanical degradation measurement, we used nanoindentation for CH3NH3PbI3-xClx perovskite films fabricated on FTO/PEDOT:PSS substrate. The hardness and elastic modulus of perovskite films were measured as a function of time. In addition, the mechanical degradation of perovskite thin films was correlated with X-ray diffraction, steady-state and time-resolved photoluminescence (PL). We also investigated the thermal instability of perovskite thin films and the irreversible performance of perovskite solar cells. Particularly, the irreversible performance of CH3NH3PbI3-xClx was analyzed by measuring the development of crystallinity, charge trapping/detrapping, trap depth, and PbI- phase while varying the temperature of perovskite films and solar cells between room temperature and 82 °C. Surprisingly, we found that the degradation of both perovskite films and solar cells occurred at ~70°C. Remarkably, even after the perovskite solar cell temperature cooled down to room temperature, the performance of solar cells continuously degraded. The underlying mechanism of irreversibly degraded performance of perovskite films and solar cells were explained in terms of the development of phase separation, increased trapping rates and deep trap depth of defect states of perovskite films.

Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells

Lead-free tin perovskite solar cells

Here, we show that flexible perovskite solar cells (PSCs) with high operational stability and power conversion efficiency (PCE) approaching 20% were achieved by elastic grain boundary (GB) encapsul...

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Electrode Design to Overcome Substrate Transparency Limitations for Highly Efficient 1 cm2 Mesoscopic Perovskite Solar Cells

Carrier Dynamics Engineering for High-Performance Electron-Transport-Layer-free Perovskite Photovoltaics

Temperature dependence of MAPbI3 films by quasi-vapor deposition technique and impact on photovoltaic performance and stability of perovskite solar cells

PTB7 as additive in Anti-solvent to enhance perovskite film surface crystallinity for solar cells with efficiency over 21%

Dual modification engineering enabled efficient perovskite solar cells with high open-voltage of 1.233 V

Passivation of defects at the surface and grain boundaries of perovskite films has become one of the most important strategies to suppress nonradiative recombination and improve optoelectronic performance of perovskite solar cells (PSCs). In this work, two conjugated molecules, abbreviated as CPT and SiPT, are designed and synthesized as the passivator to enhance both efficiency and stability of PSCs. The CPT and SiPT contain pyridalthiadiazole (PT) units, which can coordinate with undercoordinated Pb2+ at the surface and grain boundaries to passivate the defects in perovskite films. In addition, with the incorporation of CPT, the crystallized perovskite films exhibit more uniform grain size and smoother surface morphology relative to the control ones. The efficient passivation by CPT also results in better charge extraction and less carrier recombination in PSCs. Consequently, the CPT-passivated PSCs yield the highest power conversion efficiency (PCE) of 23.14 % together with better storage stability under ambient conditions, which is enhanced relative to the control devices with a PCE of 22.14 %. Meanwhile, the SiPT-passivated PSCs also show a slightly enhanced performance with a PCE of 22.43 %. Our findings provide a new idea for the future design of functional passivating molecules towards high-performance PSCs.

Perovskite solar cells have attracted extensive attention because of their photoelectric characteristics. Since 2009, the photoelectric conversion rate of the solar cells has soared from 3.8% to 25.7%. Perovskite material has become a focus of extensive academic research due to its advantages of high carrier mobility, low exciton binding energy, wide absorption spectrum and high optical absorption coefficient. However, organic P-type semiconductor material is usually used as a hole transport layer in high efficiency perovskite solar cells, for example, Spiro-OMeTAD, PEDOT:PSS, and PTAA. Because Spiro-OMeTAD is difficult to purify, many hole transport materials containing triphenylamine like Spiro-OMeTAD have been synthesized, such as triphenylamine polymer PTAA. As the conjugate parts of these triphenylamine transport materials are not coplanar and the space is distorted, they cannot form ordered stacks by spin-coating method, so their charge properties are weak, and li-TFSI and tBP are often added to improve the hole transport, so as to achieve better device effects. Moreover, the PTAA has the problem of infiltration, and it is difficult to form a completely covered perovskite film on it, which seriously affects the quality and surface morphology of perovskite film. The PEDOT:PSS itself has an acidic and corrosive electrode, and is easy to absorb moisture, which will affect the stability of the solar cell. The performance of organic material will deteriorate seriously under environmental factors such as humidity, temperature and UV irradiation, which will accelerate the aging of perovskite solar cells and become one of the main obstacles to their practical applications. In this work, the inorganic cuprous thiocyanate (CuSCN) is used as a hole transport material, the CuSCN is a rich and stable P-type semiconductor material, which has the characteristics of abundance, low cost, high carrier mobility, appropriate energy level, low defect density, good thermal stability, and excellent light transmittance. The CuSCN is one of the few known compounds with both high optical transparency (its wide band gap is 3.7–3.9 eV) and significant P-type electrical conductivity. Most importantly, CuSCN is inexpensive and can be prepared by solution method at room temperature. And its hole transport properties are improved by lithium doping. On this basis, the surface of CuSCN is modified with PTAA to avoid the interaction between CuSCN and lead iodide (PbI<sub>2</sub>), and the large-grained and dense perovskite films are prepared. Finally, the performance of perovskite solar cells is effectively improved. This work provides a reference for the preparation of the stable and efficient perovskite solar cells.

Perovskite solar cells have attracted extensive attention because of their photoelectric characteristics. Since 2009, the photoelectric conversion rate of the solar cells has soared from 3.8% to 25.7% now. Perovskite materials have become the focus of extensive academic research due to their advantages of high carrier mobility, low exciton binding energy, wide absorption spectrum and high optical absorption coefficient However, organic P-type semiconductor materials are usually used as the hole transport layer in high efficiency perovskite solar cells. For example, Spiro-OMeTAD, PEDOT: PSS, PTAA, etc. Because Spiro-OMeTAD is difficult to be purified, many hole transport materials containing triphenylamine like Spiro-OMeTAD have been synthesized, such as triphenylamine polymer PTAA. As the conjugate parts of these triphenylamine transport materials are not coplanar and the space is distorted, they cannot form ordered stacks by spin-coating method, so their charge properties are weak, and li-TFSI and tBP are often added to improve the hole transport, so as to achieve better device effects. Moreover, PTAA has the problem of infiltration, and it is difficult to form a completely covered perovskite film on it, which seriously affects the quality and surface morphology of perovskite film. PEDOT: PSS itself has an acidic and corrosive electrode, and is easy to absorb moisture, which will affect the stability of the solar cell. The performance of organic materials will deteriorate seriously under environmental factors such as humidity, temperature and UV irradiation, which will accelerate the aging of perovskite solar cells and become one of the main obstacles to their practical application. In this work, inorganic cuprous thiocyanate (CuSCN) was used as a hole transport material, CuSCN is a rich and stable P-type semiconductor material, which has the characteristics of abundant, low cost, high carrier mobility, appropriate energy level, low defect density, good thermal stability and excellent light transmittance. CuSCN is one of the few known compounds with both high optical transparency (its wide band gap is 3.7-3.9 eV) and significant P-type electrical conductivity. Most importantly, CuSCN is inexpensive and can be prepared by solution method at room temperature. And its hole transport properties were improved by lithium doping. On this basis, the surface of CuSCN was modified with PTAA to avoid the interaction between CuSCN and lead iodide (PbI<sub>2</sub>), and the preparation of large-grained and dense perovskite films was realized. Finally, the performance of perovskite solar cells was effectively improved. This work provides a reference strategy for the preparation of stable and efficient perovskite solar cells.

Achieving mixed halide perovskite via halogen exchange during vapor-assisted solution process for efficient and stable perovskite solar cells