Nontoxic pyrite iron sulfide nanocrystals as second electron acceptor in PTB7:PC₇₁BM-based organic photovoltaic cells

Abstract

Herein, we report the synthesis of nontoxic pyrite iron sulfide (FeS2) nanocrystals (NCs) using a two-pot method. Moreover, we study the influence of these NCs incorporated into the PTB7:PC71BM active layer of bulk-heterojunction ternary organic photovoltaic (OPV) cells. The OPV devices are fabricated with the direct configuration glass/ITO/PEDOT:PSS/PTB7:PC71BM:FeS2/PFN/FM. The Field’s metal (FM) is a eutectic alloy composed of 32.5% Bi, 51% In and 16.5% Sn by weight that melts at 62 °C. It is deposited on the active layer/PFN under atmospheric conditions. Ternary active layers are prepared by adding small amounts of the semiconducting FeS2 NCs at different weight ratios of 0.0, 0.25, 0.5, and 1.0 wt % with respect to the electron donor PTB7. With respect to the reference device (without FeS2), a 21% increase in the power conversion efficiency (PCE) is observed for OPVs with 0.5 wt % FeS2, such that the PCE of the OPVs is enhanced from 5.69 to 6.47%. According to the Kruskal–Wallis and Mann–Whitney statistical tests, all OPV devices follow the same trend.

Scanning Probe Microscopy Analysis of Nonfullerene Organic Solar Cells

“…The ITO-covered glass substrate cleaning and the subsequent PEDOT:PSS deposit procedure were carried out as described in a previous report. 24 For the active layer, PBDB-T was used as the electron donor and ITIC as the electron acceptor (see Figure 1a). PBDB-T and ITIC were dissolved at 1:1 w/w, 20 mg/mL in anhydrous chlorobenzene/1,8-diiodooctane (99.5:0.5 v/v) within a glove box under a nitrogen atmosphere and stirred for 24 h at room temperature.…”

“…Figure a shows the chemical structure of the used materials. The ITO-covered glass substrate cleaning and the subsequent PEDOT:PSS deposit procedure were carried out as described in a previous report . For the active layer, PBDB-T was used as the electron donor and ITIC as the electron acceptor (see Figure a).…”

“…The active layer was annealed at 160 °C for 10 min, then soaked with ethanol for 2 min and spinned at 5000 rpm for 1 min. Deposits of the electron transport layer (PFN) and top electrode (Field’s metal (FM)) were obtained as described elsewhere. − In Figure b, the final OSC structure, glass/ITO/PEDOT:PSS/PBDB-T:ITIC/PFN/FM, used in this work is schematized.…”

“…OSCs were fabricated under direct configuration, glass/ITO/PEDOT:PSS/PBDB-T:ITIC/PFN/FM, where PFN is an alcohol/water-soluble conjugated polymer used as the electron transport layer (ETL) and FM = Field’s metal is an alternative top electrode composed of Bi, Sn, and In that has been previously reported by our group. − The best PCE value was 9.2%.…”

Iron Pyrite in Photovoltaics: A Review on Recent Trends and Challenges

“…When pyrite nanocrystals were incorporated in weight ratios ranging from 0 to 1% with respect to PTB7, an increase in the PCE was observed with an optimum ratio of 0.5%. At this ratio, PCE increased from 5.69 to 6.47% (Figure a,b) which was attributed to the ability of pyrite in expediting charge dissociation and increasing pathways to charge transfer . Sharma et al also recently prepared phase-pure pyrite nanocubes and calculated the charge career properties and photovoltaic efficiency in a hybrid bulk heterojunction solar cell.…”