Analysis Of Recombination Mechanisms Research Articles

Temperature behaviour of mixed-cation mixed-halide perovskite solar cells. Analysis of recombination mechanisms and ion migration

In our study, we show that compositional engineering of the “A” site cation of ABX3 perovskite structure formed by a mix of organic and inorganic cations is an effective route to improve the thermal stability of perovskite solar cells (PSCs). In this work, mixed-cation mixed-halide PSCs have been fabricated and characterized with temperature, from 253 up to 333 K. The active layer based on CsRbFAMAPb(IBr)3 results in a more stable device compared to standard MAPbI3 devices. Electrical characterization reveals a decrease of the solar cell parameters with temperature. Using Impedance Spectroscopy (IS) characterization, we have estimated an activation energy for the halide ion migration of 0.63 ± 0.08 eV, an ion diffusion coefficient of 10−14 cm2 s−1, and a defect density of 7.27·1015 cm−3. To our knowledge, this is the first time that these parameters have been calculated in CsRbFAMAPb(IBr)3 based devices, resulting in improved values compared to MAPbI3 devices. The worsening of device performance for temperatures above 300 K is attributed to a decrease of the spiro-OMeTAD conductivity and the degradation of the perovskite/spiro-OMeTAD interface. It is shown that for low temperatures (from 253 to 323 K), Shockley-Red-Hall (SRH) recombination in the bulk governs, while for temperatures above 323 K the increase in surface recombination becomes dominant due to the presence of non-selective contacts. Numerical simulations using SILVACO ATLAS corroborate the role of SRH in the perovskite active layer for low and medium temperatures, and the crucial influence of spiro-OMeTAD transport properties in the device performance parameters.

Analysis of Recombination Mechanisms in RbF-Treated CIGS Solar Cells

In this paper, we studied the effect of rubidium fluoride (RbF) post-deposition treatment (PDT) on the properties of Cu(In,Ga)Se2 (CIGS) solar cells. Specifically, the recombination mechanisms were analyzed by a series of characterizations including thermal and optical defect spectroscopies, temperature dependent current density–voltage measurements, and time resolved photoluminescence. It was found that the main effect of RbF PDT on the solar cell was an increase of the open circuit-voltage, $V_{{\text{oc}}}$ , by 30 mV due to a decrease of the values of the diode quality factor and reverse saturation current. Recombination mechanisms were identified as being in the CIGS space charge region, likely at the grain boundaries and near the CIGS surface. Breakdown of contributions to the $V_{{\text{oc}}}$ increase showed that part of it is due to an increase of the majority carrier concentration (16 mV) and another to the increase in the minority carrier lifetime (1 mV). The latest is mostly due to a reduction in the EV+0.99 eV deep-level trap density. An additional CIGS surface modification (contributing 13 mV), observed by the secondary ion mass spectrometry, is essential to explain the full change in $V_{{\text{oc}}}$ .

Analysis of recombination mechanisms in heterojunction silicon solar cells with rapid thermally annealed thin film emitters

A new family of silicon (Si) wafer heterojunction solar cells fabricated by solid phase crystallization of PECVD amorphous silicon emitters by rapid thermal annealing (RTA) has been analyzed in order to understand the dominant recombination mechanisms. Solar cells fabricated with a broad RTA temperature range of 600–1000 °C were characterized through quantum efficiency, illuminated I–V, and capacitance–voltage measurements. Using the experimental data and theoretical considerations, the influence of carrier recombination in the quasi-neutral and space charge zones as well as at the heterojunction interface were studied. It is established that the carrier recombination in the quasi-neutral base region in the p-type Si substrate predominantly limits the device open circuit voltage. The analysis also showed that the interface recombination velocities at the heterojunction were less than 100 cm s−1. It is also qualitatively established that a post-fabrication forming gas anneal reduces the defect density at the hetero-interface.

Optimization of CdSe quantum dot concentration in P3HT:PCBM layer for the improved performance of hybrid solar cells

The improved performance of hybrid solar cells was obtained due to the effects of CdSe quantum dots (QDs) blended in the active layer. Different concentrations of CdSe QDs were mixed in the poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) based active layer. We investigated the effects of CdSe QDs on the solar cell performances by ranging its concentration from 2 to 24mg/mL. The charge transport in the active layer was improved at the optimized CdSe QDs concentration of 6mg/mL. The solar cell with pristine active layers showed a 2.98% power conversion efficiency while that with 6mg/mL CdSe QDs blended in layer showed a higher power conversion efficiency of 3.35% under AM 1.5G illumination. Analysis of recombination mechanism using the current density–voltage (J–V) characteristic at various light intensities was also performed.

Barium: An Efficient Cathode Layer for Bulk-heterojunction Solar Cells

We report Barium (Ba) cathode layer for bulk-heterojunction solar cells which enhanced the fill factor (FF) of p-DTS(FBTTh2)2/PC71BM BHJ solar cell up to 75.1%, one of the highest value reported for an organic solar cell. The external quantum efficiency exceeds 80%. Analysis of recombination mechanisms using the current-voltage (J–V) characteristics at various light intensities in the BHJ solar cell layer reveals that Ba prevents trap assisted Shockley-Read-Hall (SRH) recombination at the interface and with different thicknesses of the Ba, the recombination shifts towards bimolecular from monomolecular. Moreover, Ba increases shunt resistance and decreases the series resistance significantly. This results in an increase in the charge collection probability leading to high FF. This work identifies a new cathode interlayer which outclasses the all the reported interlayers in increasing FF leading to high power conversion efficiency and have significant implications in improving the performance of BHJ solar cells.

Experimental Investigation of Mixing Desulfurization Residues and Cement

Disposition and utilization of desulfurization residues from thermal power plants in Portland cement was investigated, controlling the content of SO3 at 3.0%(in mass), thus exploring the application feasibility of desulfurization residues in cement industry by the analysis of recombination mechanisms between desulfurization residues and Portland cement. The results show that desulfurization residues can improve physical-mechanical properties of cement: increasing the strength at various ages; improving the water requirement for normal consistency; regulating the setting time effectively, etc. Different desulfurization residues and different additions have different effects on the performance of Portland cement.

Recent writings on yeast recombination

The analysis of recombination mechanisms in Saccharomyces cerevisiae produces a lively literature spanning classical genetics, enzymology and the physical analysis of intermediates. Recent papers include excellent examples from each of these areas.