An Aggregation‐Suppressed Polymer Blending Strategy Enables High‐Performance Organic and Quantum Dot Hybrid Solar Cells

Abstract

Solution‐processing hybrid solar cells with organics and colloidal quantum dots (CQDs) have drawn substantial attention in the past decade. Nevertheless, hybrid solar cells based on the recently developed directly synthesized CQD inks are still unexplored. Herein, a facile polymer blending strategy is put forward to enable directly synthesized CQD/polymer hybrid solar cells with a champion efficiency of 13%, taking advantage of the conjugated polymer blends with finely optimized aggregation behaviors. The spectroscopic and electrical investigations on carrier transport and recombination indicate that polymer blends can endow fast carrier transport and less recombination over the single counterparts. Moreover, the blending strategy offers a “dilution effect” for top‐notch photovoltaic polymers with excessively strong aggregation tendency, resulting in moderate feature domain size and surface roughness, which afford fast hole transport and therefore high photovoltaic performance. The effectiveness of this strategy is successfully validated using two pairs of photovoltaic polymers. Accordingly, the relationships between polymer morphology, carrier transport, and photovoltaic performance are established to advance the progress of CQD/polymer hybrid solar cells. Such progress stresses that the utilization of aggregation‐suppressed polymer blends is a facile approach toward the fabrication of high‐efficiency organic–inorganic hybrid solar cells.

Brominated Polythiophene Reduces the Efficiency‐Stability‐Cost Gap of Organic and Quantum Dot Hybrid Solar Cells

“…When blended with P3HT and P3HT‐Br, we observed a clear decrease of PL intensity from PbS QDs and a significant rise in the PL intensity of polythiophene, indicating the faster carrier transport with the promising blending strategy as revealed by our recent work (Figure 1d). [ 35 ] From the above discussions, we can expect that brominated polythiophenes with lower energy levels and less aggregation can greatly enhance the photovoltaic performance to over 11%, which was the highest PCE of hybrid solar cells with polythiophenes (Figure 1e).…”

“…Despite the benefit, the device performance based on P3HT‐Br still has some gaps from those of high‐performance polymer materials. [ 39,56–58 ] To further enhance the photovoltaic performance based on polythiophenes, we employed the aggregation‐suppressed blending strategy from our recent work [ 35 ] to further improve the performance of hybrid QD and polythiophene solar cells. We first attempted to introduce the classical conjugated polymers, PM6 and poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b0]dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl)] (PTB7‐Th), which can deliver high photovoltaic performance with PbS QDs (Figure S8 and Table S3, Supporting Information).…”

“…With the increase of P3HT content, J sc and FF followed the same tendency that the values increased first and then decreased, while V oc gradually decreased (Figure 2e), which were similar to the results of our recent work. [ 35 ] Moreover, the photovoltaic performance with brominated polythiophenes has approached that with complex and high‐cost polymers, e.g., PM6 and PTB7‐Th (Figure 2f and Table 1 ). With the encouraging photovoltaic performance, we summarized the progress of hybrid QD and polythiophene solar cells and most polythiophene‐based hybrid devices can only achieve the low photovoltaic performance of ≈8% (Figure 1d and Table S4, Supporting Information).…”

“…For polythiophene blends, 0.5% 1,8‐diiooctane (DIO) was added according to our recent work. [ 35 ] Thereafter, MoO x /Ag (8 nm/120 nm) anode was thermally evaporated under low pressure (<10 −4 Pa).…”

“…[33] Subsequently, lead chalcogenide QDs are gradually on the rise, owing to the large absorption coefficients and broad and tunable absorption range (≈1400 nm), which can offer absorption complementarity with polythiophenes materials. [34][35][36][37][38] With the worldwide efforts, lead chalcogenide QDSCs have presented a PCE of 14% and retained over 90% of the initial performance after one-year ambient storage. [39,40] Moreover, PbS QDs have been reported to deliver a strikingly low cost of ≈6 $ g −1 , which exhibited a great match with lowcost polythiophene materials.…”