A review on blue phase liquid crystals: impact of dispersed guest particles on electro-optical performance and phase transitions

Blue phase liquid crystals (BPLCs) represent a promising class of soft materials for next generation electro-optical (E-O) devices due to their optical isotropy in the OFF state, submillisecond response time and tunable photonic bandgap. However, their commercial viability has been hindered by critical limitations such as narrow temperature stability, high driving voltage and large hysteresis. This review comprehensively explores recent progress in enhancing BPLC performance through strategic dispersion of nanoparticles (NPs), polymers, dyes and with novel device architectures. Significant advances, such as the extension of blue phase (BP) temperature range from ~ 2.3 °C to over 60 °C via polymer stabilization and with inclusion of the quantum dot (QD) and NPs, have been achieved. Simultaneously, average reduction in operating voltage by 50–70% was observed across several systems, including OA-LaF₃ NPs doped BPLC, where voltage dropped from 92 to 54 V. Moreover, enhancement in the Kerr constant up to 27.6% in optimized polymer networks and value exceeding 13.7 nm/V² with protrusion electrodes demonstrate improved E-O responsiveness. In addition, hysteresis value was significantly reduced from 19.2% to as low as 0.68%, while contrast ratio above 1300:1 and response time down to 9.64 µs were recorded. Into the bargain, electrode engineering strategies, such as wall shaped and vertical field switching (VFS) geometries, have enabled voltage reduction to ~ 9.5 V and doubled the decay speed relative to traditional in-plane switching (IPS) cells. Collectively, these findings reveal that through precise materials engineering and device innovation, BPLCs can overcome longstanding barriers, making them viable for practical application in displays, lasers, optical switches and photonic crystals.