Open‐Circuit Voltage Loss in Lead Chalcogenide Quantum Dot Solar Cells

Abstract

absorption coefficients, which can be used to capture the far-infrared of solar radiation. [13,14] This outperforms silicon-based and other solution-based semiconductor materials. Additionally, lead chalcogenide CQDSCs have the potential to break through the Shockley-Quesser limit, via multiple exciton generation. [15][16][17][18] In the past decade, lead chalcogenide CQDSCs have attracted abundant attention and their power conversion efficiencies (PCEs) have increased from ≈3% to ≈14%. [19][20][21] Moreover, the facile solution-processability (synthesis and ligand exchange) allows the production of solar cells by spraying, scraping, and roll-to-roll process, enabling great commercial potential. [22][23][24][25] Recently, some reports discussed the commercial viability of lead chalcogenide CQDSCs. [26,27] The results demonstrated that the cost of flexible lead chalcogenide CQDSCs can be as low as ≈0.94 $ per W, indicating the strong competitiveness of these solution-processability solar cells. To reach this low production cost, the PCEs of the CQDSCs are assumed to be 19% and the devices are assumed to be manufactured via a roll-toroll process. [27] Thus, it is still a great challenge for the commercialization of lead chalcogenide CQDSCs, and the low PCE is still the main obstacle for its market competitiveness.We summarize the main developments of lead chalcogenide CQDSCs (see Figure 1). In the early stage, the Schottky structure was used and it achieved the highest PCE of ≈5.2% in 2013. [28] But after 2014, there exist few reports of lead chalcogenide CQDSCs with the Schottky structure, due to the mismatch between optical absorption and charge extraction. [29] Subsequently, the n-p structure and depleted bulk heterojunction (DBH) structure have greatly improved the PCEs of lead chalcogenide CQDSCs. [30,31] N-p structure uses p-n junction to improve carrier extraction efficiency and reduce recombination, thus increasing the PCE of lead chalcogenide CQDSCs from ≈3% to above 9% in 2015. [19,32] Additionally, the absorption coefficient of lead chalcogenide CQDSCs reaches ≈10 6 cm −3 , which means that it is essential to use ≈1 μm solar absorber to fully absorb solar radiation. The DBH structure uses a bulk electron transport layer (ETL) to address the challenge of insufficient carrier diffusion length for the n-p structure, thus increasing the absorber thickness and greatly improving the short-circuit current (J sc ). [33][34][35] Through continued efforts, the PCE of the DBH structure has reached ≈10.8%. [36] To date, more research Lead chalcogenide colloidal quantum dot solar cells (CQDSCs) have received considerable attention due to their broad and tunable absorption and high stability. Presently, lead chalcogenide CQDSC has achieved a power conversion efficiency of ≈14%. However, the state-of-the-art lead chalcogenide CQDSC still has an open-circuit voltage (V oc ) loss of ≈0.45 V, which is significantly higher than those of c-Si and perovskite solar cells. Such high V oc loss severely limits the performance im...

Perovskite Quantum Dots in Solar Cells

“…Although the PLQY of PQDs, about 90%, [91] is much higher than bulk perovskites, about 20%, [92] and the quantum confinement effect extends the bandgap, the V OC of PQDSCs is not higher than that of bulk PSCs. In view of the V OC loss analysis of bulk perovskite and chalcogenide colloidal quantum dot solar cells via detailed balance theory, [93,94] we conclude the V OC loss of PQDSCs originating from the following factors: i) various defects form in the processes of synthesis and ligand exchange of PQDs. ii) Within the PQDs, ligands and mobile ions give rise to internal voltage drops that generate non-radiative energy loss channels.…”

Over 15% Efficiency PbS Quantum‐Dot Solar Cells by Synergistic Effects of Three Interface Engineering: Reducing Nonradiative Recombination and Balancing Charge Carrier Extraction

“…Continuous efforts of various modifications of the CQD/CQD, ETL/CQD, and CQD/HTL interfaces have led to the incremental rise in PCE of PbS CQDSCs to a reported 14%. [ 13,14 ] Modification of the CQD/CQD interface: for example, complete surface passivation of PbS CQDs via cascade modifications and the fabrication of QD bulk heterojunction films with balanced carrier transport (PCE ≈ 13.3%); [ 4b ] and the introduction of monolayer perovskite bridges between adjacent CQDs to significantly improve carrier mobility (PCE ≈ 13.8%). [ 4a ] Modification of the ETL/CQD interface: for example, passivating the surface of ZnO NCs with halide ion (PCE ≈ 11.6%) [ 15 ] or adding a buffer layer such as In 2 O 3 between ZnO/CQD (11.1%) [ 16 ] to minimize surface defect densities, establish a favorable electronic band alignment, and increase charge transfer ability.…”

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

“…Owing to high flexibility and favorable solution processing, [1][2][3][4][5] organic solar cells (OSCs) have witnessed unprecedented With the aim to accelerate the commercialization progress of OSCs and CQD solar cells, hybrid strategy holds promising potential to be leveraged for the further improvement of OSC stability and CQD performance. [27] Over the past five years, PbS CQD/organic hybrid solar cells with bilayer structure have made great progress with the great efficiency advance from ≈5% to >13%. [24,[28][29][30][31][32][33][34] Recently, Kim et al successfully synthesized a diketopyrrolopyrrole-based polymer with high hole mobility and favorable energy level with PbS CQDs.…”