All‐polymer solar cells (all‐PSCs) based on n‐ and p‐type polymers have emerged as promising alternatives to fullerene‐based solar cells due to their unique advantages such as good chemical and electronic adjustability, and better thermal and photochemical stabilities. Rapid advances have been made in the development of n‐type polymers consisting of various electron acceptor units for all‐PSCs. So far, more than 200 n‐type polymer acceptors have been reported. In the last seven years, the power conversion efficiency (PCE) of all‐PSCs rapidly increased and has now surpassed 10%, meaning they are approaching the performance of state‐of‐the‐art solar cells using fullerene derivatives as acceptors. This review discusses the design criteria, synthesis, and structure–property relationships of n‐type polymers that have been used in all‐PSCs. Additionally, it highlights the recent progress toward photovoltaic performance enhancement of binary, ternary, and tandem all‐PSCs. Finally, the challenges and prospects for further development of all‐PSCs are briefly considered.

High-performance ternary all-polymer solar cells with outstanding efficiency of 9.0% are realized by incorporating two donor and one acceptor polymers with complementary absorption and proper energy level alignment.

To explore the advantages of emerging all‐polymer solar cells (all‐PSCs), growing efforts have been devoted to developing matched donor and acceptor polymers to outperform fullerene‐based PSCs. In this work, a detailed characterization and comparison of all‐PSCs using a set of donor and acceptor polymers with both conventional and inverted device structures is performed. A simple method to quantify the actual composition and light harvesting contributions from the individual donor and acceptor is described. Detailed study on the exciton dissociation and charge recombination is carried out by a set of measurements to understand the photocurrent loss. It is unraveled that fine‐tuned crystallinity of the acceptor, matched donor and acceptor with complementary absorption and desired energy levels, and device architecture engineering can synergistically boost the performance of all‐PSCs. As expected, the PBDTTS‐FTAZ:PNDI‐T10 all‐PSC attains a high and stable power conversion efficiency of 6.9% without obvious efficiency decay in 60 d. This work demonstrates that PNDI‐T10 can be a potential alternative acceptor polymer to the widely used acceptor N2200 for high‐performance and stable all‐PSCs.

High efficiency and mechanical robustness are both crucial for the practical applications of all‐polymer solar cells (all‐PSCs) in stretchable and wearable electronics. In this regard, a series of new polymer acceptors (PAs) is reported by incorporating a flexible conjugation‐break spacer (FCBS) to achieve highly efficient and mechanically robust all‐PSCs. Incorporation of FCBS affords the effective modulation of the crystallinity and pre‐aggregation of the PAs, and achieves the optimal blend morphology with polymer donor (PD), increasing both the photovoltaic and mechanical properties of all‐PSCs. In particular, an all‐PSC based on PYTS‐0.3 PA incorporated with 30% FCBS and PBDB‐T PD demonstrates a high power conversion efficiency (PCE) of 14.68% and excellent mechanical stretchability with a crack onset strain (COS) of 21.64% and toughness of 3.86 MJ m‐3, which is significantly superior to those of devices with the PA without the FCBS (PYTS‐0.0, PCE = 13.01%, and toughness = 2.70 MJ m‐3). To date, this COS is the highest value reported for PSCs with PCEs of over 8% without any insulating additives. These results reveal that the introduction of FCBS into the conjugated backbone is a highly feasible strategy to simultaneously improve the PCE and stretchability of PSCs.

No abstract

A new strategy for designing ternary solar cells is disclosed in this contribution. We select a low bandgap polymer named PTB7-Th and a high band gap polymer named PBDTTS-FTAZ sharing the same bulk ionization potential and interface positive integer charge transfer energy while featuring complementary absorption spectra. They are used to fabricate efficient ternary solar cells, where the hole can be transported freely between the two donor polymers and collected by the electrode as in one broadband low bandgap polymer. Furthermore, the fullerene acceptor is chosen so that the energy of the positive integer charge transfer state of the two donor polymers is equal to the energy of negative integer charge transfer state of the fullerene, enabling enhanced dissociation of all polymer donor and fullerene acceptor excitons and suppressed bimolecular and trap assistant recombination. The Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff)) Published online: ((will be filled in by the editorial staff)) combining two donor polymers with same bulk and interface energy which make the hole transportation like in one donor polymer. The voltage losses was minimized due to EICT+ ≈ EICT−, where the trade-off between enhancing of charge generation and charge recombination by ICT states arrives sweet spot.

The development of efficient and biocompatible organic near-infrared emitters is attractive for many applications, spanning from photodynamic therapy [1] to light fidelity (Li-Fi) all-optical networking systems. [2][3][4] In particular, the range 700-1000 nm is interesting for medical applications, given the semitransparency of biological tissue in this spectral interval, [5] and we will specifically refer to this range as near-infrared (NIR) in the following text. Compared to conventional inorganic materials, organic NIR emitters are interesting also for their mechanical conformability, which makes them appealing for the integration in flexible and stretchable devices. [6] Furthermore, the metal-free organic light-emitting materials can be a cheap and biocompatible alternative to inorganic ones for application in wearable, implantable, or in vivo medical applications, such as for sensing of body temperature, heart and respiration rates, blood pressure, glucose level, and oxygenation. [7] In the search for ever-higher efficiencies, several classes of materials have been investigated, such as perovskite-structured methylammonium lead halides, [8][9][10] quantum dots, [11] and organometallic phosphorescent complexes. [12][13][14][15][16][17][18][19] However, although such hybrid materials afford substantial electroluminescence (EL) external quantum efficiency (EQE) in the NIR, in some cases exceeding 10% [8,10] or even 20% or so, [13] their use of heavy, toxic, and/or costly metals is not ideal for manufacturing, sustainability, environmental impact, and, in perspective, biocompatibility. Furthermore, in such hybrid systems, and in general in materials that leverage triplet excitons to boost the EQE, [20,21] exciton recombination dynamics typically fall in the hundreds of nanoseconds or even in the microsecond (or longer) range, which intrinsically limits the bandwidth when integrated in devices for telecommunications. For Li-Fi applications, [2][3][4] fluorescent molecular and polymeric materials are preferred, given that the typical fluorescence lifetime of these materials is of the order of few nanoseconds or less, thereby ideally allowing data transmission rates up to the Gb s −1 regime.In the last decade, scientists have attempted different strategies to develop heavy-metal-free NIR fluorescent organic light-emitting diodes (OLEDs), with chemical design essentially revolving around the careful combination of donor and acceptor groups to both tune the spectral range (up to 1000 nm) and maximize the EQE. [22][23][24][25][26][27][28][29][30][31][32][33] Very recently, we have, for Due to the so-called energy-gap law and aggregation quenching, the efficiency of organic light-emitting diodes (OLEDs) emitting above 800 nm is significantly lower than that of visible ones. Successful exploitation of triplet emission in phosphorescent materials containing heavy metals has been reported, with OLEDs achieving remarkable external quantum efficiencies (EQEs) up to 3.8% (peak wavelength > 800 nm). For OLEDs incorporating f...

High-photovoltage all-PSCs with good stability were realized by using a new polymer acceptor based on diketopyrrolopyrrole–isoindigo.