Fully non-fused acceptors with alkylsilyl side-chains for efficient indoor organic photovoltaics

Abstract

The tetrathienoacene (4T) based fully non-fused acceptors exhibit excellent indoor-spectrum compatibility and cost competitiveness, positioning them as ideal candidates for indoor organic solar cells (OSCs). We develop two low-cost 4T-core fully non-fused acceptors featuring alkylsilyl side chains for indoor OSCs. By elongating the length of side chains from methyl to ethyl, the resulting acceptor, 4T-SiE-4F, adopts a planar molecular configuration, improves blend film crystallinity and decreases the total density of states by 32% from 4.7 × 10¹⁵ to 3.2 × 10¹⁵ cm⁻³ eV⁻¹. Concurrently, it also effectively improves charge transport with hole mobility increasing by 21%, form 3.15 × 10⁻⁴ to 3.81 × 10⁻⁴ cm² V⁻¹ s⁻¹ and electron mobility increasing by 49% from 2.49 × 10⁻⁴ to 3.71 × 10⁻⁴ cm² V⁻¹ s⁻¹ in the blend films. Consequently, an efficient and low-cost indoor photovoltaic device with a power conversion efficiency of 21.41% is developed based on D18:4T-SiE-4F. Our work establishes a design framework for efficient and economically viable indoor organic photovoltaics.