Device physics of van der Waals heterojunction solar cells

Abstract

Heterostructures based on atomically thin semiconductors are considered a promising emerging technology for the realization of ultrathin and ultralight photovoltaic solar cells on flexible substrates. Much progress has been made in recent years on a technological level, but a clear picture of the physical processes that govern the photovoltaic response remains elusive. Here, we present a device model that is able to fully reproduce the current-voltage characteristics of type-II van der Waals heterojunctions under optical illumination, including some peculiar behaviors such as exceedingly high ideality factors or bias-dependent photocurrents. While we find the spatial charge transfer across the junction to be very efficient, we also find a considerable accumulation of photogenerated carriers in the active device region due to poor electrical transport properties, giving rise to significant carrier recombination losses. Our results are important to optimize future device architectures and increase power conversion efficiencies of atomically thin solar cells.

Exciton physics and device application of two-dimensional transition metal dichalcogenide semiconductors

“…This penalty is lower in multilayer structures than in monolayers. In addition, poor carrier transport properties [140] and inefficient carrier extraction at the contacts can lead to pile-up of photocarriers in the device and recombination losses. For all these reasons, power conversion efficiencies in TMD-based photovoltaic devices have as yet remained below the theoretical limit for their respective band gaps.…”

Diverse Atomically Sharp Interfaces and Linear Dichroism of 1T' ReS2‐ReSe2 Lateral p–n Heterojunctions

“…A series of group VI‐TMD‐based lateral heterojunctions and even superlattices (such as MoS 2 ‐MoSe 2 , MoS 2 ‐WSe 2 , and MoS 2 ‐WS 2 ‐MoS 2 ‐WS 2 ), which possess highly symmetry hexagonal (2H) structure, have been successfully synthesized via single‐step, two‐step, or multi‐step growth strategies . The structure modulation and energy‐band engineering at the atomic‐scale interface of the lateral heterojunction, where many exciting new physic properties and applications have been explored, is the key goal of these research works . However, most of the heterojunctions studied at present are based on the 2H TMDs, the study to distorted octahedral (1T') structure TMD‐based heterojunctions that would have distinct interface structures and properties is seldom reported.…”

Emerging solar cells energy trade-off: Interface engineering materials impact on stability and efficiency progress

“…Moreover, OSC efficiency related V oc optimization route several factors are involved to active‐interface architecture . M. M Furchi et al, very recent report on van der Waals 2D HJ model has claimed 25% efficiency . From theoretic and research reports summarization, it is pertinent to notify that interface size impacts on electric to thermal domains conduction disparity that is vital for instability.…”