Origin of the effects of PEG additives in electrolytes on the performance of quantum dot sensitized solar cells

Review of recent progress in the development of electrolytes for Cd/Pb-based quantum dot-sensitized solar cells: performance and stability

Quantum dot-sensitized solar cells (QDSSCs) represent an exciting advancement in third-generation photovoltaic solar cells owing to their ability to generate multiple electron-hole pairs per photon, high stability under light and moisture exposure, and flexibility in size and composition tuning. Although these cells have achieved power conversion efficiencies exceeding 15%, there remains a challenge in enhancing both their efficiency and stability for practical large-scale applications. Therefore, in this review, we aimed to investigate recent progress in improving the long-term stability, analyzing the impact of advanced quantum dot properties on charge-transport optimization, and assessing the role of interface engineering in reducing recombination losses to maximize QDSSC performance and stability. Additionally, this review delves into key elements such as the electrolyte composition, ionic conductivity, and compatibility with counter electrodes and photoanodes to understand their influence on power conversion efficiencies and stability. Finally, potential directions for advancing QDSC development in future are discussed to provide insights into the obstacles and opportunities for achieving high-efficiency QDSSCs.

Improving the efficiency of quantum dot-sensitized solar cells by increasing the QD loading amount

In quantum dot-sensitized solar cells (QDSCs), optimized quantum dot (QD) loading mode and high QD loading amount are prerequisites for great device performance. Capping ligand-induced self-assembly (CLIS) mode represents the mainstream QD loading strategy in the fabrication of high-efficiency QDSCs. However, there remain limitations in CLIS that constrain further enhancement of QD loading levels. This review illustrates the development of various QD loading methods in QDSCs, with an emphasis on the outstanding merits and bottlenecks of CLIS. Subsequently, thermodynamic and kinetic factors dominating QD loading behaviors in CLIS are analyzed theoretically. Upon understanding driving forces, resistances, and energy effects in a QD assembly process, various novel strategies for improving the QD loading amount in CLIS are summarized, and the related functional mechanism is established. Finally, the article concludes and outlooks some remaining academic issues to be solved, so that higher QD loading amount and efficiencies of QDSCs can be anticipated in the future.

Efficient quantum dot-sensitized solar cells through sulfur-rich carbon nitride modified electrolytes

For quantum dot sensitized solar cells (QDSSCs), modifying conservative polysulfide electrolytes with polymer additives has been proven as an effective method to control charge recombination processes at the TiO₂/QDs/electrolyte interface and to accomplish efficient cell devices. In this respect, the polysulfide electrolyte is modified with polymeric and sulfur-rich graphitic carbon nitride (SGCN) to enhance the photovoltaic performance of QDSSCs. For the first time, SGCN is used to passivate surface trap states and act as the steric hindrance between TiO₂/QDs/electrolyte interfaces. The QDSSCs fabricated with GCN and SGCN additives exhibited higher efficiencies, especially improved short-circuit current (J_SC) and fill factors (FFs) than those of the liquid electrolyte. Cu-In-S sensitized QDSSCs constructed with GCN and SGCN additives exhibited efficiencies of 6.73% and 7.13%, respectively, whereas the liquid electrolytes delivered an efficiency of 6.16%. Additionally, the applicability of SGCN additives in various Cu-based QDSSCs to enhance their photovoltaic performance is further verified using Cu-In-Se QDSSCs. An increase in the conversion efficiencies of QDSSCs with SGCN additives is possibly due to (1) their electron-rich surface which can act as an obstacle for electron-hole recombination, thereby suppressing the back-transfer of photo-induced electrons to the QD/electrolyte interface; (2) SGCN facilitates the reduction of S_n^2- to S^2- redox couple, thus providing holes towards the QDs/electrolyte more efficiently. Overall, this work provides an innovative and economic additive to modify polysulfide electrolytes, thereby controlling the TiO₂/QDs/electrolyte interfaces of QDSSCs.

Poly(acrylamide-co-acrylic acid) gel polymer electrolyte incorporating with water-soluble sodium sulfide salt for quasi-solid-state quantum dot-sensitized solar cell

Rapid decay of photoanode, leakage from sealant, and evaporation of electrolyte are always the major concerns of quantum dot-sensitized solar cells (QDSCs) based on liquid electrolyte. Subsequently, gel polymer electrolyte (GPE) appears as an attractive solution in addition to lower cost, lighter weight, and flexibility. Poly(acrylamide- co-acrylic acid) (PAAm-PAA) is of special interest to act as a polymer host to entrap liquid electrolyte because it provides high transparency, good gelatinizing properties, and excellent compatibility with the liquid electrolyte. In this work, the electrical and transport properties of PAAm-PAA GPE incorporating with water-soluble sodium sulfide were characterized by impedance spectroscopy. An increment of ionic conductivity was observed with the incorporation of ethylene carbonate (EC) and potassium chloride (KCl). The highest room temperature ionic conductivity of PAAm-PAA GPE is 70.82 mS·cm−1. QDSC based on PAAm-PAA GPE with the composition of 1.3 wt% of KCl, 0.9 wt% of EC, 55.3 wt% of PAAm-PAA, 38.5 wt% of sodium sulfide, and 4.0 wt% of sulfur can present up to 1.80% of light-to-electricity conversion efficiency.