The power conversion efficiency (PCE) of a ternary organic solar cell (TOSC) with an active layer consisting of PBDB‐T‐2F and two non‐fullerene materials Y6 and SF(BR)4 is simulated. Tungsten disulphide (WS2) is used as the hole transport layer (HTL) to reduce the contact resistance between the active layer and anode which enhances the internal quantum efficiency to 91.7%. It is found that the use of a highly absorbing non‐fullerene small molecule acceptor, SF(BR)4, enhances the absorption as well as improves the stability. Finally, the incorporation of the graded refractive index coating, in the form of moth‐eye shaped nanostructures, on the top of glass reduces the reflection losses and enhances the transmission coefficient from 0.88 to 0.94. Thus, the TOSC simulated here, of the structure moth‐eye‐AR/glass/ITO/WS2/PBDB‐T‐2F:Y6:SF(BR)4/PFN‐Br/Al, produces a PCE of 20.87%. The results presented in this paper are expected to provide useful guidance for fabricating highly efficient and stable hybrid bulk‐heterojunction solar cells.

An alternative approach to simulate the power conversion efficiency (η PCE) of bulk heterojunction organic solar cells (BHJ OSCs), as a product of efficiencies of absorption (η abs), dissociation (η dis), and extraction (η ext), is presented. Although η abs and η dis do not directly contribute to the simulation of η PCE , the approach enables us in understanding their roles in optimizing the power conversion efficiency of BHJ OSCs. This method is applied to simulate η PCE as a function of the thickness of active layer for three different BHJ OSC structures, one with a fullerene acceptor and two with two different nonfullerene acceptors. The results are found to be in good agreement with those from the previous simulation and experimental works and are expected to be useful in optimizing the thickness of the active layer.

In this paper, characterisation of exciton generation is carried out in three bulk-heterojunction organic solar cells (BHJ OSCs)—OSC1: an inverted non-fullerene (NF) BHJ OSC; OSC2: a conventional NF BHJ OSC; and OSC3: a conventional fullerene BHJ OSC. It is found that the overlap of the regions of strong constructive interference of incident and reflected electric fields of electromagnetic waves and those of high photon absorption within the active layer depends on the active layer thickness. An optimal thickness of the active layer can thus be obtained at which this overlap is maximum. We have simulated the rates of total exciton generation and position dependent exciton generation within the active layer as a function of the thicknesses of all the layers in all three OSCs and optimised their structures. Based on our simulated results, the inverted NF BHJ OSC1 is found to have better short circuit current density which may lead to better photovoltaic performance than the other two. It is expected that the results of this paper may provide guidance in fabricating highly efficient and cost effective BHJ OSCs.

The power conversion efficiency (PCE) of a hybrid bulk hetero-junction organic solar cell with an active layer of a blend of PBDT TS1 (donor) and PCBM (acceptor) incorporated with copper zinc tin sulfide (CZTS) quantum dots (QDs) and zinc oxide (ZnO) nanowires is simulated. It is found that the incorporation of CZTS-QDs of a single radius (1.5 nm) enhances the PCE from 9.1% to 12.34% and of 13 different radii CZTS-QDs elevates PCE to 14.96%. This enhancement occurs mainly due to the enhancement in absorption that enhances short-circuit current density (J sc ) and fill factor (FF). Finally, a layer of ZnO nanowires is added on top of the glass to reduce the reflection losses and absorption of ultraviolet light in the active layer that causes degradation and reduces the stability of organic solar cells (OSCs). The hybrid structure, thus simulated, has an enhanced PCE of 16.32% and is expected to be relatively more stable. It is expected that the results of this simulation may inspire all researchers interested in the fabrication of highly efficient hybrid OSCs.

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