On the Mechanistic Understanding of Photovoltage Loss in Iron Pyrite Solar Cells

Abstract

Considering the natural abundance, the optoelectronic properties, and the electricity production cost, iron pyrite (FeS2) has a strong appeal as a solar cell material. The maximum conversion efficiency of FeS2 solar cells demonstrated to date, however, is below 3%, which is significantly below the theoretical efficiency limit of 25%. This poor conversion efficiency is mainly the result of the poor photovoltage, which has never exceeded 0.2 V with a device having appreciable photocurrent. Several studies have explored the origin of the low photovoltage in FeS2 solar cells, and have improved understanding of the photovoltage loss mechanisms. Fermi level pinning, surface inversion, ionization of bulk donor states, and photocarrier loss have been suggested as the underlying reasons for the photovoltage loss in FeS2. Given the past and more recent scientific data, together with contradictory results to some extent, it is timely to discuss these mechanisms to give an updated view of the present status and remaining challenges. Herein, the current understanding of the origin of low photovoltage in FeS2 solar cells is critically reviewed, preceded by a succinct discussion on the electronic structure and optoelectronic properties. Finally, suggestions of a few research directions are also presented.

Ferromagnetism in a Semiconductor with Mobile Carriers via Low-Level Nonmagnetic Doping

“…[21][22][23][24] It is also noteworthy that Na x CoO 2 is also an excellent oxide thermoelectric. [25] Here we show that cubic pyrite β-FeS 2 , which is a common mineral and a known semiconductor, thought to be suitable for applications, [26][27][28][29][30][31], particularly optoelectronic devices such as solar cells, [32][33][34][35][36] can be made magnetic by suitable p-type doping and that it has properties consistent with spintronic applications. Importantly, although FeS 2 contains a magnetic element, it is diamagnetic, meaning that it does not contain Fe moments in its ordinary state.…”

Near‐Infrared Photoactive Semiconductor Quantum Dots for Solar Cells

“…Pyrite FeS 2 is also a member of NBG semiconductors with a reasonable bandgap of 0.95 eV and large absorption coefficient (α > 6 × 10 5 cm −1 for hν > 1.3 eV). [180] Recently, SnS and FeS 2 QDs have been utilized as light harvesters in both heterojunction and sensitized solar cells. [60] Despite yielding relatively low PCEs, it is expected that a thorough evaluation of factors causing the low V oc is high essential to boost the performance of SnS and FeS 2 QDSCs.…”

“…During this process, the mid-gap states would cause the loss of carriers prior to the successful extraction through nonradiative recombination. [164,180] Since efficient charge extraction requires photogenerated electrons and holes transport to the corresponding electrodes within their lifetimes, L dif should be longer than the quasi-neutral-region width in a planar device. [235] Moreover, during the carrier collection process, the factors, such as the resistance of materials, the frequency hopping of electrons at the interfaces, and the contact condition between the semiconductor material and the metal, will result in the recombination of carriers and the leakage of currents.…”

Accurate Prediction of Band Structure of FeS2: A Hard Quest of Advanced First-Principles Approaches

“…Despite progress towards understanding the origin of the low V OC in pyrite FeS 2 ( Rahman et al, 2020 ), consensus is still not reached on the fundamental band gaps of the two FeS 2 phases. Experimentally, values varying from 0.6 to 2.6 eV have been reported for pyrite, primarily due to differences in sample preparation, measuring technique, and analytical model of spectra used in experimental studies ( Ferrer et al, 1990 ; Ennaoui et al, 1993 ).…”