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Soft robots often show a superior power-to-weight ratio using highly compliant, light-weight material, which leverages various bio-inspired body designs to generate desirable deformations for life-like motions. In this letter, given that most material used for soft robots is light-weight in general, we propose a volumetrically enhanced design strategy for soft robots, providing a novel design guideline to govern the form factor of soft robots. We present the design, modeling, and optimization of a volumetrically enhanced soft actuator (VESA) with linear and rotary motions, respectively, achieving superior force and torque output, linear and rotary displacement, and overall extension ratio per unit volume. We further explored VESA's proprioceptive sensing capability by validating the output force and torque through analytical modeling and experimental verification. Our results show that the volumetric metrics hold the potential to be used as a practical design guideline to optimize soft robots’ engineering performance

Deeply understanding of the performance discrepancy of hole-transporting materials (HTMs) in perovskite solar cells (PSCs) with different configuration (inverted or direct) is important for designing efficient HTMs. Herein, three organic HTMs TZ1, TZ2, and TZ3 have been employed to fabricate the inverted PSCs. Optoelectronic properties and photovoltaic performance of these HTMs are investigated. TZ3 featuring the 3,6-di(thiophen-2-yl)thieno[3,2-b]thiophene conjugate bridge shows a higher work function and enhanced capability of hole extraction, achieving a higher power conversion efficiency (PCE) of 16.33% in the inverted PSCs. Importantly, results reveal that the conjugate bridge has a relevant effect on the photovoltaic performance of cells with different device configuration. The PCE trend of TZ1, TZ2, and TZ3 in inverted PSCs is diametrically opposed to that of direct devices. We proposed that linear triphenylamine HTMs contain a fused bridge with high degree of conjugation are good choice for the direct PSCs. On the other hand, it is better to incorporate linear triphenylamine HTMs with deep highest occupied molecular orbital (HOMO) toward the inverted PSCs, because the photovoltage plays a crucial role in the efficiency of the inverted PSCs. This systematic study provides a new viewpoint to design HTMs toward PSCs with different device configuration.

In this work, four new truxene-based hole-transporting materials (HTMs) have been synthesized and applicated in the inverted perovskite solar cells (PSCs). The impact that the length of alkyl and periphery arylamine on the photophysical, electrochemical and hole transporting properties has been systematically investigated. These new HTMs exhibit decent hole mobility of 10−3 cm2 V−1 s−1, which ensure efficient hole extraction in dopant-free devices. PSC using the dopant-free M118 achieves a power conversion efficiency of 17.1%, which is much higher than the value of 14.4% achieved using poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). Importantly, PSCs based on these truxene HTMs exhibit significantly enhanced durability under UV light. This work reveals that the adjustment of length of alkyl as well as periphery arylamine is necessary for development of stable and efficient truxene HTMs.

The core plays a crucial role in achieving high performance of linear hole transport materials (HTMs) toward the perovskite solar cells (PSCs). Most studies focused on the development of fused heterocycles as cores for HTMs. Nevertheless, nonfused heterocycles deserve to be studied since they can be easily synthesized. In this work, we reported a series of low-cost triphenylamine HTMs (M101-M106) with different nonfused cores. Results concluded that the introduced core has a significant influence on conductivity, hole mobility, energy level, and solubility of linear HTMs. M103 and M104 with nonfused oligothiophene cores are superior to other HTMs in terms of conductivity, hole mobility, and surface morphology. PSCs based on M104 exhibited the highest power conversion efficiency of 16.50% under AM 1.5 sun, which is comparable to that of spiro-OMeTAD (16.67%) under the same conditions. Importantly, the employment of M104 is highly economical in terms of the cost of synthesis as compared to that of spiro-OMeTAD. This work demonstrated that nonfused heterocycles, such as oligothiophene, are promising cores for high performance of linear HTMs toward PSCs.