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Simple and low-cost two-dimensional (2D) materials are of great interest considering their wide use in various device applications. Here, we present the application of 2D materials, i.e., graphene oxide (GO), molybdenum disulfide (MoS 2), and tungsten disulfide (WS 2) as hole transport layer (HTL) in non-fullerene acceptors (NFAs) organic photovoltaics (OPVs) using device simulation. The numerical simulation was carried out using SCAPS-1D and specifically focused on the effect of thickness and defect density at the active layer on the photovoltaic characteristics of the devices. In addition, the influence of defect density at the HTL/active layer interface on the device performance was also studied. After conducting a series of optimization, an optimum power conversion efficiency (PCE) of 15.89%, 20.05%, and 23.55% was achieved for NFA-based OPV with GO, MoS 2 , and WS 2 , respectively. This work provides a practical explanation of the feasible performance enhancement and critical design parameters for OPV devices. The results showcase the potential application of 2D materials as low-cost HTL for high-efficiency organic solar cells. [Display omitted] • Device modelling 2D – HTM of non-fullerene acceptor organic photovoltaic was comprehensively performed. • The influence of physical parameters on NFA – OPVs performance was thoroughly discussed. • After optimization, we obtained PCE of 15.89%, 20.05%, and 23.55% for GO, MoS 2 , and WS 2 as HTM, respectively. • The study promotes future OPVs optimization and performance enhancement. [ABSTRACT FROM AUTHOR]

This study explores the optimization of hole transport material (HTM)-free perovskite solar cells featuring laminated free-standing carbon film as a back electrode. Surface treatment of perovskite film using different types of solvent (chlorobenzene, toluene, and ethyl acetate) was carried out to improve the electrical contact at the carbon/methylammonium lead iodide interface. Overall, the surface treatment improved mechanical adhesion between the perovskite and carbon film. The conductivity of the free-standing carbon electrode was further improved by attaching the carbon film to various types of conductive support. Our results show that the selection of both solvents used during surface treatment and the type of conductive substrate has a considerable impact on the resulting performance, wherein all modifications gave rise to substantial improvement over the benchmark unmodified carbon electrode. A power conversion efficiency (PCE) of 7.74% was achieved by the perovskite solar cell with laminated carbon electrode on Al foil combined with the application of chlorobenzene as surface treatment, demonstrating a tremendous increase in performance compared to that of untreated free-standing carbon electrode that produced PCE less than 1%. The main contributor to the improved performance is presumably due to the low carrier recombination rate and improved charge carrier extraction as implied by the electro-impedance spectroscopy and photoluminescence analysis. This work demonstrates a facile approach for resolving the challenges in developing low-cost HTM-free perovskite solar cells with a free-standing carbon film electrode. [Display omitted] • Optimization of HTM-free PSCs with free-standing carbon electrode is reported. • The effects of solvent treatment and the use of conductive support are investigated. • Surface treatment improves electrical contact at carbon and perovskite interface. • Combined use of chlorobenzene surface treatment and Al foil produced the best result. [ABSTRACT FROM AUTHOR]

Semi-transparent (ST) tandem organic solar cells (OSCs) are typically exhibiting a trade-off between efficiency and average visible transmittance (AVT), which can be minimized by the appropriate selection of transparent contacts and absorbing materials in the sub-cells. Herein, we demonstrate efficient and highly transparent hetero-tandem OSCs constructed by stacking PBDT[2F]T:PC 71 BM and PCE10:PC 61 BM active layers as front-cell and back-cell, respectively. Optical and electrical simulations show that the PBDT[2F]T and PCE10-based sub-cells possess potential as ST and reflective tandem OSCs. With the aid of the simulations, we could fabricate reflective tandem OSCs with an efficiency of up to 8.3%. Furthermore, a ST tandem OSC, employing conductive silver nanowire top contact, achieved an AVT of 49.2%, efficiency of 5.3%, and high light utilization efficiency (LUE) of 2.61% under 1 sun, AM1.5G spectral illumination. This study demonstrates the importance of the sub-cells choices for developing ST tandem solar cells with a good balance of AVT and PCE, paving the way for solar windows of high performance. [Display omitted] • Optical and electrical simulations performed to aid reflective and semi-transparent tandem OSCs fabrication. • Fabrication of tandem based on PBDT[2F]T:PC 71 BM and PCE10:PC 61 BM blends with PCE higher than their single-cells (8.2%). • Semi-transparent tandem device with a very high AVT of nearly 50%, in agreement with optical simulation. • The semi-transparent tandem based on PBDT[2F]T:PC 71 BM and PCE10:PC 61 BM blends achieved high PCE of 5.3% and LUE of 2.61%. [ABSTRACT FROM AUTHOR]