Characterising Exciton Generation in Bulk-Heterojunction Organic Solar Cells

Abstract

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.

An asymmetric A–DA′D–π-A type non-fullerene acceptor for high-performance organic solar cells

“…Organic solar cells (OSCs) have attracted much attention during the past several years due to their intrinsic advantages, such as being lightweight and flexible, having roll-to-roll processing capacity, etc. [1][2][3][4][5][6] In the past several decades, fullerene-derivative acceptors have become prevalent in the field of OSCs. However, the inherent drawbacks of fullerene derivatives, such as their narrow and weak absorption, nonadjustable energy levels, poor stability, etc., have limited further improvements in the photovoltaic performances of OSCs.…”

Optimizing Device Structure of PTB7-Th:PNDI-T10 Bulk Heterojunction Polymer Solar Cells by Enhancing Optical Absorption

“…where N t,sur f is the density of the surface traps, V bi is the built-in voltage (it is calculated from the difference of work functions of Aluminum (Al) and PEDOT:PSS for the conventional OSC (0.8 eV) and Al and MoO 3 for the inverted OSC (1.1 eV)), and V cor represents the corrected voltage and it is obtained as [35]:…”

“…Peterson et al [34] also used the optical transfer matrix method earlier to model the short-circuit photocurrent action spectra of poly(3-(4 -(1",4",7"trioxaoctyl)phenyl)thiophene) (PEOPT)/fullerene (C 60 ) bilayer structure OSC and estimated the exciton diffusion length to be 4.7 nm and 7.7 nm in PEOPT and C 60 , respectively. Studies involving the optical modelling of OSCs are mostly focused on polymer-fullerene devices using OTMM and drift diffusion equations to simulate the parameters such as short circuit current density (J SC ) and open circuit voltage (V oc ) [35,36].…”

Operating Temperature of Nonfullerene Acceptor‐Based Bulk Heterojunction Organic Solar Cells

“…(NF) acceptor materials with highly tunable energy levels have recently been developed. [10,16,17] NF BHJ OSCs fabricated using p-type conjugated polymers as the donor and n-type small molecules as the acceptor have consistently demonstrated steady progress, outperforming PCBMbased BHJ OSCs and reaching theoretical and experimental efficiencies of 20% [18] and 18%, [19] respectively, in 2020. The PCE of a BHJ OSC depends basically on the four parameters, the light intensity, open-circuit voltage (V OC ), short-circuit current density ( J SC ), and fill factor (FF), as: PCE ¼ V oc J sc FF P in , where P in is the incident solar power.…”