High-brightness picosecond green lasers are important for precision processing and advanced manufacturing, yet lithium triborate (LBO)-based picosecond second-harmonic generation often faces a trade-off between brightness and temperature bandwidth. Here we treat the longitudinal phase-mismatch trajectory as a design degree of freedom and propose a brightness-oriented adiabatic trajectory that jointly optimizes conversion efficiency and beam quality. Through parametric trajectory screening and longitudinal temperature-profile mapping, the proposed trajectory was implemented in a 50-mm-long LBO crystal. Experiments produced 79.87 W of picosecond green output at 532.286 nm, corresponding to a light-to-light conversion efficiency of 62.4%, with a beam quality factor of ${M}^2=1.24$. Compared with a conventional efficiency-oriented adiabatic trajectory, the proposed trajectory increased brightness by suppressing beam quality degradation rather than maximizing conversion efficiency alone. We further introduce the brightness temperature bandwidth, which reached 25°C for the proposed trajectory, 39% larger than the 18°C value obtained with the conventional trajectory, but smaller than the corresponding efficiency temperature bandwidth of 34°C. This difference indicates that an efficiency-defined bandwidth can overestimate the practically usable operating range.