Solar, Volume 2, Issue 3 (September 2022) – 4 articles

Ternary planar heterojunction organic solar cells (PHJ-OPVs) were fabricated using three organic small molecules, alpha-sexithiophene (α-6T), aluminum phthalocyanine chloride (AlPcCl) and fullerene (C₆₀). These molecules can be easily sublimated under a vacuum; they have complementary optical absorption spectra and their energy band structure alignment is favorable for electronic charge transfers. Moreover, α-6T and AlPcCl have almost the same HOMO, which is desirable to avoid any decrease in open circuit voltage. The AlPcCl intercalated layer bridges the energy levels of the electron donor, α-6T, and the electron acceptor, C₆₀, which facilitates charge transport through the energy cascade effect. Moreover, the charge carrier mobility measurements of AlPcCl, using the space charge limited current method, demonstrated that it iss ambipolar. All these properties combine to improve the power conversion efficiency (PCE) of PHJ-OPVs by moving from binary structures (α-6T/C₆₀, α-6T/AlPcCl and AlPcCl/C₆₀) to ternary ones (α-6T/AlPcCl/C₆₀). We show, in this study, that both interfaces of the ternary PHJ-OPVs are efficient for carrier separation. After optimization of the different layer thickness, we show that, by comparing the optimum efficiencies of the binary PHJ-OPVs, the realization of ternary PHJ-OPVs, based on the active layers α-6T/AlPcCl/C₆₀, using the following optimized method, allows us to achieve a PCE of 4.33%. Full article

The study compares the performance of satellite-based datasets and the Ångström–Prescott (AP) model in estimating the daily global horizontal irradiance (GHI) for stations in South Africa. The daily GHI from four satellites (namely SOLCAST, CAMS, NASA SSE, and CMSAF SARAH) and the Ångström–Prescott (AP) model are evaluated by validating them against ground observation data from eight radiometric stations located in all six macro-climatological regions of South Africa, for the period 2014-19. The evaluation is carried out under clear-sky, all-sky, and overcast-sky conditions. CLAAS-2 cloud fractional coverage data are used to determine clear and overcast sky days. The observed GHI data are first quality controlled using the Baseline Surface Radiation Network methodology and then quality control of the HelioClim model. The traditional statistical benchmarks, namely the relative mean bias error (rMBE), relative root mean square error (rRMSE), relative mean absolute error (rMAE), and the coefficient of determination (R²) provided information about the performance of the datasets. Under clear skies, the estimated datasets showed excellent performance with maximum rMBE, rMAE, and rRMSE less than 6.5% and a minimum R² of 0.97. In contrast, under overcast-sky conditions there was noticeably poor performance with maximum rMBE (24%), rMAE (29%), rRMSE (39%), and minimum R2 (0.74). For all-sky conditions, good correlation was found for SOLCAST (0.948), CMSAF (0.948), CAMS (0.944), and AP model (0.91); all with R2 over 0.91. The maximum rRMSE for SOLCAST (10%), CAMS (12%), CMSAF (12%), and AP model (11%) was less than 13%. The maximum rMAE for SOLCAST (7%), CAMS (8%), CMSAF (8%), and AP model (9%) was less than 10%, showing good performance. While the R2 correlations for the NASA SSE satellite-based GHI were less than 0.9 (0.896), the maximum rRMSE was 18% and the maximum rMAE was 15%, showing rather poor performance. The performance of the SOLCAST, CAMS, CMSAF, and AP models was almost the same in the study area. CAMS, CMSAF, and AP models are viable, freely available datasets for estimating the daily GHI at South African locations with quantitative certainty. The relatively poor performance of the NASA SSE datasets in the study area could be attributed to their low spatial resolution of 0.5° × 0.5° (~55 km × 55 km). The feasibility of the datasets decreased significantly as the proportion of sky that was covered by clouds increased. The results of the study could provide a basis/data for further research to correct biases between in situ observations and the estimated GHI datasets using machine learning algorithms. Full article

Quantum dot solar cells have received significant attention in comparison to standard solar cells because of their hybrid nature, low production costs, and higher power conversion efficiency. Although quantum dot solar cells (QDSCs) have several benefits over ordinary solar cells, their performance lags due to carrier combination within the quasi-neutral region (QNR). The electron transport layer (ETL) and hole transport layer (HTL) are the two layers that have the most effect on QDSC performance. This numerical analysis is carried out by using the Solar Cell Capacitance Simulator-1 dimensional software (SCAPS-1D). In this paper, the optimization of two different device structure investigations is performed. In this proposed device structure, WS₂ and IGZO are used as two ETL, CdS is used as a buffer layer, Sb₂Se₃ is used as an absorber layer, and PbS as HTL. Initially, the optimization of the device has been performed, followed by depth analysis of the doping densities. Resistance analysis is also performed to illustrate the effect of resistance on the device. Further, the impact of temperature on the device parameters is also represented, followed by a contour plot between thickness and bandgap for both devices. The impact of the series and shunt resistance on the performance of the solar cell is investigated. The effect of temperature is studied further, and it is observed that the solar device is temperature-sensitive. Finally, the optimized performance with IGZO ETL with PCE of 20.94% is achieved. Full article

Low-bandgap mixed tin (Sn)–lead (Pb) perovskite solar cells have been extensively investigated in the past few years due to their great potential in high-performance perovskite/perovskite tandem solar cells. From this perspective, we briefly summarize the mechanism of understanding of additives and the advances in the efficiency and stability of such low-bandgap Sn-Pb perovskite materials and solar cells in terms of various effective strategies for suppressing the defects and oxidation of Sn²⁺, regulating crystallization growth, etc. We then provide a perspective regarding the achievement of high-quality, low-bandgap Sn-Pb perovskites and highly efficient solar cells. Full article