Contributions of Charge Generation Versus Transport to Photocurrent in Dilute-Donor Organic Solar Cells with Non-fullerene Acceptors

Abstract

The photocurrent generation in dilute donor organic solar cells (DDOSCs) based on fullerene and non-fullerene acceptors is compared. The donor concentration is kept under 5 wt % to avoid the formation of a percolation pathway for hole transport, as verified by studying the hole mobilities in an insulating polymer matrix. The short-circuit current densities (J sc ) in DDOSCs for three common acceptors are quantified in terms of charge generation, transport, and collection, which are probed using ideal J sc calculated from the transfer matrix method, hole mobility measured from space charge limited current method, and charge collection efficiency, respectively. Using non-fullerene acceptors improves both charge generation and transport, with charge transport being more important in determining J sc in DDOSCs.

Development of fullerene acceptors and the application of non-fullerene acceptors in organic solar cells

“…There are also many competitive non-fullerene acceptor materials, among which the NFA PDI has high stability and low material cost, and in these years, the performance of OSC devices has taken a remarkable step forward, which are based on monomeric PDI acceptors, with PCEs up to more than 12%, and current research targeting monomeric PDI acceptors is working toward addressing the barriers of fill-factor values and moderate-short current density (J(sc)) [35]. There is also a non-fullerene A-DA'D-A-type acceptor (Figure 1C), with an absorption spectrum complementary to the donor and good transport properties, mainly due to its fusion backbone centered on a trapezoidal electron-deficient nucleus [36].…”

Extremely Non-Equilibrium Hopping Transport and Photogeneration Efficiency in Organic Semiconductors: An Analytic Approach

“…Organic semiconductors are already widely used in organic light-emitting diodes, and extensive research continues for their applications in photovoltaics and other organic electronics devices. − Despite the enormous diversity of structure and optoelectronic characteristics, organic semiconductors, including both low-molecular materials and polymers, share common transport properties, such as the hopping nature of transport of charge carriers and excitations, as well as structural and associated energy disorder. It is the latter that determines the strong temperature and field dependence of mobility in disordered organic semiconductors, according to the Gaussian disorder model .…”